Tandem axle assemblies are widely used on trucks and other load-carrying vehicles. The tandem axle assembly typically comprises a front axle and a rear axle. The tandem axle assembly may be designated a 6×4 tandem axle assembly when the front axle and the rear axle are drivingly engaged. The tandem axle assembly may be designated a 6×2 tandem axle assembly when either one of the front axle and the rear axle is drivingly engaged.
The 6×4 tandem axle assembly provides improved traction for road conditions having reduced traction, such as when the vehicle must traverse mud, ice, or snow. The 6×4 tandem axle assembly also provides improved traction when the operator applies an increased amount of torque to the front axle and the rear axle. Despite the benefits of improved traction, a fuel economy of the vehicle including the 6×4 tandem axle assembly is typically lower than a fuel economy of a vehicle including the 6×2 tandem axle assembly.
A tandem axle assembly may be configured to permit an operator of a vehicle or a control system of the vehicle to switch from a 6×4 mode of operation to a 6×2 mode of operation (or from the 6×2 mode of operation to the 6×4 mode of operation) as required by operating conditions. The tandem axle assembly able to switch operating modes as desired by the operator requires the operator to initiate a shifting procedure. The tandem axle assembly may also be able to switch operating modes using a control system utilizing a controller or a plurality of controllers which monitors a variety of parameters, which typically include a rotational speed of a drive shaft and a rotational speed of an axle to determine the operating mode for the vehicle and then initiate the shifting procedure.
It would be advantageous to develop a distributed hierarchical control system for a tandem axle assembly of a vehicle capable of performing a shifting procedure in an automatic manner or as desired by an operator of the vehicle without excessively increasing a cost and a complexity of the tandem axle assembly.